Sequential Cesium Incorporation for Highly Efficient Formamidinium-Cesium Perovskite Solar Cells

03 January 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Although pure formamidinium iodide perovskite (FAPbI3) possesses an optimal gap for photovoltaics, their poor phase stability limits the long-term operational stability of the devices. A promising approach to enhance their phase stability is to incorporate cesium into FAPbI3. However, state-of-the-art formamidinium-cesium (FA-Cs) iodide perovskites demonstrate much worse efficiency compared with FAPbI3, limited by different crystallization dynamics of formamidinium and cesium, which result in poor composition homogeneity and high trap densities. We develop a novel strategy of crystallization decoupling processes of formamidinium and cesium via a sequential cesium incorporation approach. As such, we obtain highly reproducible and highly efficient solar cells based on FA1-xCsxPbI3 films, with uniform composition distribution and low defect densities. In addition, our cesium-incorporated perovskites demonstrate much enhanced stability compared with FAPbI3, as a result of suppressed ionic migration due to reduced electron-phonon coupling.


FA-Cs perovskite
Sequential Cs Incorporation
crystallization decoupling engineering


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